The present invention relates to a liquid check valve, and more particularly to a small compact check valve to prevent backflow.
When forcing liquid into a pipe line, it is necessary to check back flow. Thus when forcing liquid forward by means of a pump, a back flow cycle occurs. Therefore, to feed liquid during the forward forcing cycle, checking back flow is necessary at the loading point. If there is no forcing cycle, it is necessary to provide some checking means for the purpose of always keeping liquid in stability in the pipe line. Various kinds of check valves have been conventionally used. However, the prior art valves are complicated in construction, and to disassemble the valve is troublesome. When providing such check valves in pipe lines, one of the requirements is to cause no loss of flowing pressure, and for this purpose the caliber of the valve seat should be equivalent to, or more than the bore of the pipe line, and the diameter of the disc valve piece is inevitably larger than the bore of pipe line. The use of such a large disc or valve section in the valve body does not permit a ready fit in the hole portion of the corresponding pipe line on both sides of the valve body. It is necessary to mount the valve assembly in a direction crossing the pipe line and, the fitting used to open the disc valve has a diameter which is larger than that of the pipe line. Further this fitting for the disc valve piece requires a cover and a gasket. The disc valve piece inserted in this way, is rotatably installed by means of arms in the rotary seat in the pipe opening, and the cover for the opening is held by a plurality of bolts and nuts. Therefore the conventional arrangement requires a lot of components such valve bodies, covers, disc valves, valve seats, disc valve seats, arms, hinges, washers, plugs, gaskets, nuts and bolts, and moreover the valve bodies are fairly large, the inner constructions are complicated and the construction is not easy, and it takes considerable troubles and skill for factories to control many such parts and to make them. It is natural that the cost is high, and moreover such complicated systems have disadvantages so that check valves do not always work smoothly in the course of operations. Efforts have been made to cancel those defects. Thus, ball valve have been used for example, which are rotated in the valve body. To insert such a ball valve into the valve body, the valve body, is divided into two parts, which are held by a plurality of screws, and further a special structure is required which allows the ball valve to press smoothly to the valve seat in the valve body which is larger than the ball valve.